The overall objective of this research is the specification of the dynamic (time-varying) acoustic information that is used by listeners to identify vowels in their normal context, that is, when they are coarticulated with consonants in continuous speech. The research speaks to a very broad questions of continuing importance in speech and hearing research: What acoustic information in the speech signal is used by listeners to identify the phonetic message?" Traditional theories and many current models of vowel perception emphasize the role of static acoustic "targets" as the major source of information about vowel identity. However, much current research has shown that listeners rely critically on dynamic information that is available in the changing acoustic pattern of syllables (format trajectories) when they try to identify coarticulated vowels. Four types of studies will be performed: 1) Perceptual studies with electronically-modified natural speech materials will be conducted to investigate the perception of vowels in different phonetic contexts and at different speech rates. 2) Alternative auditory-perceptual representations of format trajectories will be studied to examine their relative efficacy in accounting for the perception of coarticulated vowels. 3) Format trajectories in synthetic consonant-vowel-consonant syllables will be manipulated to test alternative hypotheses about the perceptual relevane of spectral and temporal parameters characterizing "style of change". 4) Studies of the perception of coarticulated German vowels (by native and non-native speakers) will be conducted to assess the generality across languages of the findings about the role of dynamic acoustic information in the perception of vowels.